摘要
从靖边潜台奥陶系马五段主要岩石类型出发，综合分析沉积特征和地球化学特征，认为靖边潜台奥陶系存在三种白云化作用：（1）泥粉晶云岩与硬石膏共生，形成于盐度较高的局限蒸发潮坪，为准同生白云化所形成；（2）粗粉品厶岩分伽较局限，夹于与硬石膏共生的泥粉晶云岩层之间，不与硬石膏共生，但低有序度和略富钙的特征表明其为回流渗透白云化成因；（3）岩溶风化壳较发育区的孔洞缝中大量次生方解石的残余组构表明，去白云化之前的白云石以细砂晶为主，多为自形、半自形菱面体，部分具有环带构造和“亮边雾心”，形成温度为52．30℃～78．05℃，碳氧同化素特征与典型的埋藏白云石较接近，说明其为浅-中埋藏环境下形成的白云石。这三种白云化作用中，准同生白厶化是最主要最普遍的白云化类型，其次是浅-中埋藏白云石，回流渗透白云化分布较局限。明确马五。亚段的白云化类型，对于重建岩相古地理、研究储层的形成机理、提高勘探的成功率有重要意义。
In Jingbian platform, Ordovician Majiagou 5 member is an important natural gas reservoir in Changqing oil- field. But there exists a long argument about its dolomitization type. This issue has been discussed on the basis of Ma- jiagou 54 sub-member. In this paper, after researching the sedimentary and geochemical characteristics of different rock types, the authors draw a conclusion that penecontemporaneous, reflux and burial dolomitization are main dolo- mitization types in this region. （1） Micritic and silt-sized crystal dolomite which is always associated with anhydrite, deposited in restricted and evaporative tidal flat with high salinity, and formed by penecontemporaneous dolomitiza- tion. （2） Coarser silt-sized crystal dolomite is distributed among the layers of micritic and silt-sized crystal dolomite with anhydrite, and its coarser crystal grain, lower degree of order and slightly richer calcium show that this type dolo- mite is formed by reflux dolomitization. （3） Much secondary calcite is spread in karst layer, and the metasomasis re- sidual texture shows that the grain size of the dolomite before dedolomitization is mainly fine crystal, partially with eu- hedral-subhedral texture, zonal structure, and bright border with vague center. Their inclusion temperature span is from 52.30 ℃ to 78.05℃, and the characteristics of carbon and oxygen isotopes are more similar to typical burial dol- omites. All these indicate that the dolomite before dedolomitization is formed in shallow and middle-depth burial diage- netic environment. Clarifying the dolomitization type of Majiagou 54 sub-member is very important to rebuild lithofacies palaeogeographic, research the reservoir formation mechanism, and improve the success possibility of exploration.
出处
《沉积学报》
CAS
CSCD
北大核心
2014年第1期110-117,共8页
Acta Sedimentologica Sinica
基金
国家自然科学基金项目(批准号:41172105)
湖北省自然科学基金(编号:2011CDB002)联合资助
关键词
准同生白云化
回流渗透白云化
埋藏白云化
靖边潜台
马五4亚段
penecontemporaneous dolomitization
reflux dolomitization
burial dolomization
Jingbian Platform
Ma- jiagou 54 Sub-member
